know the real nature of realities of another kind, viz. of appearances. Again, in this form of the view, it may be possible to vindicate Kant's doctrine that the distinction between the real and the illusory is tenable within what we know, for it may be possible to distinguish within appearances between a 'real' appearance[11] and an 'illusory' appearance.[12]' [9] 'Things' is substituted for 'the reality which we believe to exist independently of perception' in order to conform to Kant's language. The substitution, of course, has the implication--which Kant took for granted--that the reality consists of a plurality of individuals. [10] 'Things in themselves' has here to be substituted for 'things as they are in themselves' in the statement of the negative side of the position, in order to express the proper antithesis, which is now that between two things, the one known and the other unknown, and not that between two points of view from which one and the same thing is known and not known respectively. [11] _Erscheinung._ [12] _Schein._ An implication of this defence should be noticed. The issue relates to the nature of space[13], and may be stated in terms of it. For, since space is a presupposition of all other properties which the non-philosophical consciousness attributes to physical things, it makes no difference whether we say that things _only appear_ heavy, hard, in motion, &c., or whether we say that things _only appear_ spatial. In the same way it is a matter of indifference whether we say that, though things are not heavy, hard, &c., their appearances are so, or whether we say that, though things are not spatial, their appearances are so. The issue, then, concerns the possibility of maintaining either that things only appear spatial, or that the appearances which they produce are spatial, while the things themselves are not, or, at least cannot be known to be, spatial. [13] We might add time also; but, for a reason which will appear later (p. 139), it can be neglected.